Yes. All Airbnb rental income is taxable in the UK, regardless of whether hosting is your main income or a side project. HMRC treats it as property income and expects you to report it via Self Assessment. There are two exceptions where you may not need to report at all: if your total gross property income is £1,000 or less (covered by the Property Income Allowance), or if you let a furnished room in your own home and earn £7,500 or less (covered by Rent-a-Room Relief). Outside of these thresholds, you must register for Self Assessment and file a return.